Spectroscopic characterization of zinc oxide nanorods synthesized by solid-state reaction

Well-crystallized zinc oxide nanorods have been fabricated by single step solid-state reaction using zinc acetate and sodium hydroxide, at room temperature. The sodium lauryl sulfate (SLS) stabilized zinc oxide nanorods were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. The X-ray diffraction revealed the wurtzite structure of zinc oxide. The size estimation by XRD and TEM confirmed that the ZnO nanorods are made of single crystals. The growth of zinc oxide crystals into rod shape was found to be closely related to its hexagonal nature. The mass ratio of SLS:ZnO in the nanorods was found to be 1:10 based on the thermogravimetric analysis. Blue shift of photoluminescence emission was noticed in the ZnO nanorods when compared to that of ZnO bulk. FT-IR analysis confirmed the binding of SLS with ZnO nanorods. Apart from ease of preparation, this method has the advantage of eco-friendliness since the solvent and other harmful chemicals were eliminated in the synthesis protocol.     

Thermally induced polytype transformations among the layered double hydroxides (LDHs) of Mg and Zn with Al

The hydrotalcite-like layered double hydroxide (LDH) of Mg with Al shows dramatic changes in the peaks arising from the (h0l)/(0kl) family of reflections in its powder X-ray diffraction pattern during thermal treatment. DIFFaX simulations show that these changes arise due to the transformation of the disordered 3R1 polytype into the 1H polytype on dehydration. The 1H polytype is an essential precursor to the decomposition reaction, which results in the formation of an oxide residue with the rock salt structure. In contrast, the LDH of Zn with Al does not undergo any such transformation, retaining the structure of the 3R1 polytype until decomposition into the oxide residue. Given the poor octahedral site preference of the Zn2+ ion, the 1H polytype is neither structurally stable nor is it topochemically necessary for the thermal decomposition of the Zn-Al LDH, the end product of the decomposition reaction being an oxide with the wurtzite structure.     

Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

The isothermal decomposition of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature leads to the formation of Co₃O₄. The phase evolution during the decomposition process was monitored using powder X-ray diffraction. The transformation of cobalt hydroxide to cobalt oxide occurs via three phase mixture while cobalt hydroxynitrate to cobalt oxide occurs through a two phase mixture. The nature of the sample and its preparation method controls the decomposition mechanism. The comparison of topotactical relationship between the precursors to the decomposed product has been reported in relation to polytypism.     

氧化镁两步法制备阻燃型氢氧化镁

以氯化镁焙烧生成的氧化镁为原料,采用两步法即先水化后水热的方法制备出六方片状氢氧化镁。考察了水化时间、水热时间和温度及水热添加剂氢氧化钠浓度对氢氧化镁材料形貌的影响。研究表明,水化时间超过3 h,氧化镁水化率基本不变,水热温度越高对晶体形貌改善越大,水热时间的延长可促进晶体粒径及厚度的增加,但是对晶体的宽厚比改变不大。水热添加剂氢氧化钠浓度的增加可明显地提高晶体结晶度,减小晶体微观内应变,提高粉体分散性。     

氧化镁两步法制备阻燃型氢氧化镁

以氯化镁焙烧生成的氧化镁为原料,采用两步法即先水化后水热的方法制备出六方片状氢氧化镁。考察了水化时间、水热时间和温度及水热添加剂氢氧化钠浓度对氢氧化镁材料形貌的影响。研究表明,水化时间超过3h,氧化镁水化率基本不变,水热温度越高对晶体形貌改善越大,水热时间的延长可促进晶体粒径及厚度的增加,但是对晶体的宽厚比改变不大。水热添加剂氢氧化钠浓度的增加可明显地提高晶体结晶度,减小晶体微观内应变,提高粉体分散性。     

Enolates de l'acetylacetate d'ethyle. Structure et reactivite du sel de potassium en presence d'ether couronne et de cryptand

It is shown that, through the addition of 18-crown-6 or cryptand (2.2.2) to potassium ethyl acetoacetate enolate solutions in tetrahydrofuran, 1:1 complexes are formed. A single crystal of the 1:1 potassium énolate-18-crown-6 complex has been obtained. Its structure has been determined by X-ray diffraction. The crystal includes entities formed from an enolate anion chelating a potassium cation externally complexed by the crown-ether. The vibrational spectrometry shows that the structure of the entity is kept in solution. In the species formed through the addition of cryptand (2.2.2), the enolate anion has a structure (IR spectroscopy) and a reactivity very close to that of the free anion, observed in a dissociating solvent (DMSO, HMPA). When crown ether is added, a contact ion pair is formed, in which the cation is externally solvated by the crown. On the other hand, the cation encapsulation by the cryptand leads to a released anion with an “ S-trans” or “W” structure. The reactivity and the orientation of the alkylation reactions of these entities have been measured in THF solutions. They are discussed in relation to the structure of the species present in the reaction medium.     

Epoxydation d'aldehydes et de cetones par un procede de transfert solide-liquide

The condensation reaction of trimethylsulfonium iodide with variously functionalized aldehydes and ketones in the presence of solid potassium hydroxide in acetonitrile leads to the selective formation of the corresponding epoxides in high yields. The method used calls upon a solid-liquid transfer process.     

Structural and phase changes in iron(III)—aluminium(III) mixed hydroxide—oxide system; A thermoanalytical study

The structural and phase changes occurring in the ferric hydroxide gel, alumina gel and the coprecipitated ferric—aluminium hydroxide—oxide system are studied by thermoanalytical and X-ray diffraction techniques. The conversion of hydrated ferric oxide to hematite takes place through γ-Fe₂O₃ and alumina gel to oxide occurs through hydrargellite, bohemite as intermediate. The occurrence of solid solutions below 10 mole % of alumina, i.e. interstitial solid solution up to 1.5 mole %, then substitutional solid solution up to 3.43 mole % and thereafter separation of phases is observed. For higher concentrations of alumina, zones enriched in either hydrated iron oxide or aluminum oxyhydroxide are noticed.     

Effect of Various Synthesis methods on the Electrochemical Properties of LiNi1/3Co1/3Mn1/3O2

Layered LiNi1/3Co1/3Mn1/3O2 has the isostructure of α-NaFeO2 and shows high rate capacity with stable cycleability. Furthermore, the thermal behavior of this material is milder than that of lithium nickel oxide and lithium cobalt oxide. In addition, it is expected to be stable at elevated temperatures. Therefore LiNi1/3Co1/3Mn1/3O2 may be the most promising cathode materials of lithium-ion secondary battery.In this research, LiNi1/3Co1/3Mn1/3O2 was prepared by solid-state reaction, sol-gel method and mixed hydroxide method. The influences of synthesis method on the physical and electrochemical properties of LiNi1/3Co1/3Mn1/3O2 were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), charge/discharge cycling cyclic voltammetry and differential scanning calorimetry (DSC). XPS studies show that the predominant oxidation states of Ni, Co and Mn in the LiNi1/3Co1/3Mn1/3O2 compound are 2+, 3+ and 4+. From the voltage profile and cyclic voltammetry, the redox processes occurring at ～3.8V and ～4.5V are assigned to the Ni2+/Ni3+ and Co3+/Co4+ couples, respectively. Different preparation methods result in the difference in morphology (shape, particle size and specific surface area) and electrochemical behaviors. A sample prepared by solid-state reaction has the worst electrochemical performance among these three methods. Sample synthesized by mixed hydroxide method displays the better rate capacity than that prepared by sol-gel method, while the capacity retention of sample prepared by sol-gel method is superior to that synthesized by mixed hydroxide method.     

尺寸可控氢氧化镧纳米棒的水热合成及表征

以硝酸镧为镧源、三乙胺为碱源和络合剂,通过简便的水热法成功合成了大量均一的氢氧化镧纳米棒。详细研究了三乙胺的用量、表面活性剂、反应温度和时间对产物形貌及尺寸的影响。基于实验结果,提出了氢氧化镧纳米棒的形成机理。同时制备了稀土掺杂的氢氧化镧纳米棒。利用X射线衍射（XRD）、透射电子显微镜（TEM）、选区电子衍射（SAED）和高分辨透射电子显微镜（HRTEM）对所得产物的物相、结构和形貌进行了表征分析。     

Preparation and characterization of zinc oxide nanoflakes using anodization method and their photodegradation activity on methylene blue

In this work, we report the formation of leaf-like ZnO nanoflakes by anodization of zinc foil in a mixture of ammonium sulfate and sodium hydroxide electrolytes under various applied voltage and concentration of sodium hydroxide. The morphology and structure of ZnO nanoflakes were investigated by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. In addition, the photocatalytic activity of the prepared nanoflakes zinc oxide was evaluated in the photodegradation of organic dye methylene blue (MB) solution under UV irradiation. It was found that zinc oxide prepared under high concentration of sodium hydroxide and high voltage showed better performance in the photodegradation of methylene blue.     

Dosage direct de submicrotraces de bore dans la soude de purete analytique par la methode fluorimetrique a l'hydroxy-2-methoxy-4-chloro-4'-benzophenone

A method based on the highly sensitive fluorescent reaction of boric acid with 2-hydroxy-4-methoxy-4'-chlorobenzophenone (H.M.C.B.), is described for the direct determination of traces of boron in “analytical grade” sodium hydroxide. In the nanogram range, the reliability of the H.M.C.B. method is satisfactory; the fluorescent reaction is not affected by up to 8% (v/v) of water. The sample is dissolved directly in concentrated sulfuric acid and no preliminary separation is needed. Interferences from other impurities of sodium hydroxide are negligible. Results for five different “analytical grade” reagents were: (0.9±0.2)·10^-6,(3.2±0.3)·l0^-6,(3.2±0.3)·^-6, (4.0±0.4)·10^-6and(2.0±0.16)·10^-6% B.     

一步法水热合成 TiO2纳米线及其光催化性能

以钛酸丁酯和异丙醇为原料, 采用一步法在NaOH溶液中水解后直接进行水热反应, 经焙烧处理, 得到TiO2纳米线. 采用扫描电子显微镜(SEM)、X射线衍射(XRD)和能谱分析(EDX)对产物进行了形貌、结构及成分的表征. 考察了不同水热温度、碱液浓度、水热反应时间及焙烧温度等因素对产物的影响. 结果表明, 获得较好形貌TiO2纳米线的最佳水热温度、碱液浓度和水热反应时间分别是180 ℃, 10 mol/L和24 h. 所得TiO2纳米线焙烧至950 ℃时仍为锐钛矿相, 说明本文制备方法迟滞了TiO2纳米线由锐钛矿相向金红石相的转变. 以甲基橙为目标降解物, 采用紫外-可见分光光度计研究了未掺杂和铕掺杂TiO2纳米线(Eu-TiO2)的光催化性能. 结果显示, 最佳掺铕量(摩尔分数)为1.6%. 在300 W紫外灯照射60 min时, 此掺铕量的TiO2纳米线对甲基橙溶液的降解率是未掺杂样品的1.5倍.     

纳米氧化锌的合成与表征

纳米氧化锌的合成与表征何勇宁，沈孝良，马礼敦（复旦大学分析测试中心上海２００４３３）关键词纳米材料，氧化锌，合成，表征制备纳米材料的方法很多，如蒸发冷凝法、化学气相沉积法、溶胶－凝胶法、超临界法、水热法及各种热分解法等。Ｌｉｕ等［２］用超声雾化热分解...     

Évolution thermique d'un hydroxyde de nickel lamellaire mal organisé avec des molécules d'eau en insertion entre les feuillets: comparaison avec l'hydroxyde de nickel cristallisé Ni(oH)2

The authors have studied the thermal decomposition of a turbostratic nickel hydroxide by means of DTA, TGA and isothermal analysis. The turbostratic compound has been described as a random stacking of parallel and equidistant nickel hydroxide layers with intercalary water layers.Well crystallized Ni(OH)₂ has been used as reference. The preparation and the main properties of both hydroxides have been indicated. It was found that the removal of intercalary water takes place simultaneously with the removal of hydroxyl groups at a temperature, not very different from the dehydration temperature of Ni(OH)₂. NO₃^? ions from the starting material and trapped water have been found on the dehydration product. The very fine nickel oxide shows a quite important increase of the lattice parameter (4.215 instead of 4.177 Å). A reversible variation of the inter-layer spacing from 8.5 to 7Å has been pointed out when the turbostratic hydroxide is heated up to 150°C.     

Nitrosation of alkenes by nitric oxide: Crystal structures of bis-(1-nitroso-2-nitro-cyclohexane) and bis-(1-nitroso-2-nitro-1-phenylethane)

The reaction of nitric oxide with alkenes has been studied. Crystal structures have been established by X-ray diffraction studies for bis-(1-nitroso-2-     

Ferric hydroxide supported gold subnano clusters or quantum dots: enhanced catalytic performance in chemoselective hydrogenation

An attempt to prepare ferric hydroxide supported Au subnano clusters via modified co-precipitation without any calcination was made. High resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed to study the structure and chemical states of these catalysts. No Au species could be observed in the HRTEM image nor from the XRD pattern, suggesting that the sizes of the Au species in and on the ferric hydroxide support were less than or around 1 nm. Chemoselective hydrogenation of aromatic nitro compounds and alpha,beta-unsaturated aldehydes was selected as a probe reaction to examine the catalytic properties of this catalyst. Under the same reaction conditions, such as 100 degrees C and 1 MPa H2 in the hydrogenation of aromatic nitro compounds, a 96-99% conversion (except for 4-nitrobenzonitrile) with 99% selectivity was obtained over the ferric hydroxide supported Au catalyst, and the TOF values were 2-6 times higher than that of the corresponding ferric oxide supported catalyst with 3-5 nm size Au particles. For further evaluation of this Au catalyst in the hydrogenation of citral and cinnamaldehyde, selectivity towards unsaturated alcohols was 2-20 times higher than that of the corresponding ferric oxide Au catalyst.     

Synthese en milieu hydrothermal et caractérisation de l'oxyhydroxyde de vanadium V3+OOH et d'une nouvelle variété allotropique du dioxyde VO2

Vanadium oxyhydroxide containing mostly trivalent vanadium was synthesized under hydrothermal conditions at 200°C and 2 k bar by hydrolysis of NaVO₃ previously reduced under hydrogen. The structure of VOOH is of diaspore type, isotypic with A1OOH. Oxidation of VOOH at 80°C in air gives in a few days a new metastable phase of vanadium dioxide VO₂; the structure of this new phase is also of the diaspore type, the transformation VOOH → VO₂ being topotactic. Characterization of these phases was done by X-ray diffraction, thermogravimetry, and magnetic, and electrical measurements. Both phases show semiconductor behavior and no electronic transition is observed in VO₂ (diaspore) up to 200°C.     

Morphological and Thermal Investigations of the ‘Active’ Dimer Hydroxide of Chromium(III)

The ‘active’ dimer hydroxide, [Cr₂(μ-OH)₂(OH)₄(OH₂)₄]·2 H₂O, has been characterised by means of IR spectroscopy, thermal analysis, X-ray powder diffraction, and electron microscopy. Thermogravimetric measurements and the Cr content of the hydroxide are in agreement with this composition. The IR spectrum supports the notion that this hydroxide is composed of unaltered dimer fragments linked through hydrogen bonds of ca. 2.8 Å. The compound is microcrystalline in nature with an X-ray powder diffraction pattern distinctly different from that of the isomeric ‘active’ monomer hydroxide. Electron micrographs of the ‘active’ dimer hydroxide indicate that this material consists of platelets the sie of which is dependent on the pH of precipitation.     

A Facile Room Temperature Synthesis of Zinc Oxide Nanostructure and Its Influence on the Flame Retardancy of Poly Vinyl Alcohol

In this work, poly vinyl alcohol–ZnO nanocomposites were synthesized via two different in situ and ex-situ methods. In ex-situ, at first zinc oxide nanostructures were synthesized by one-step precipitation reaction between zinc acetate and sodium hydroxide. The effect of different surfactants such as poly vinyl pyrrolidone, poly vinyl alcohol and poly ethylene glycol on the morphology of ZnO nanostructures was investigated. Nanostructures were characterized by X-ray diffraction, scanning electron microscopy. The influence of ZnO nanostructures on the flame retardancy of the poly vinyl alcohol matrix was studied using underwriter laboratories UL-94 analysis.